This Error event indicates that the Microsoft Exchange Server 2010 transport routing engine can't find the route to the specified information store on the specified Mailbox server. Therefore, routing is unable to deliver messages to recipients with mailboxes located in this store. This error may be caused by Active Directory replication latency.

To resolve this warning, do one or more of the following:

• Use the Get-ExchangeServer cmdlet in the Exchange Management Shell to verify that the specified server exists.
  
  
• Take no action. The messages will be routed to the Unreachable queue and delivery will be retried when routing configuration changes. When the server information is updated in routing tables, the messages will automatically be routed to the destination server.
  
  
• If you have been granted the correct permissions, you can force Active Directory replication to occur immediately. An Active Directory notification will cause the routing tables to be updated and any affected messages in the Unreachable queue will be resubmitted and routed to the destination server.
  
  
• Verify that the Microsoft Information Store service is started on the Mailbox server that is specified in the error message text.
  
  
• Verify that the databases within the information store that is specified in the error message text are mounted. For more information, see How to Mount a Database.
  
  
• Verify that the Exchange server specified in the error message text is functional and available on the network. For example, use the Ping or PathPing command-line tools to test basic connectivity. Use Ping to isolate network hardware problems and incompatible configurations. Use PathPing to detect packet loss over multiple-hop trips. For more information, see Microsoft Knowledge Base article 325487, How to troubleshoot network connectivity problems.
  
  
• Verify that the Exchange server that logged this event can communicate with one or more Active Directory servers available in the organization.
  
  
• Review the Application log and System log on your Exchange 2010 servers for related events. For example, events that occur immediately before and after this event may provide more information about the root cause of this error.
  
  
• Resolve your issue by using self-support options, assisted support options, and other resources. You can access these resources from the Exchange Server Solutions Center. From this page, click Self-Support Options in the navigation pane to use self-help options. Self-help options include searching the Microsoft Knowledge Base, posting a question at the Exchange Server forums, and others. Alternatively, in the navigation pane, you can click Assisted Support Options to contact a Microsoft support professional. Because your organization may have a specific procedure for directly contacting Microsoft Technical Support, be sure to review your organization's guidelines first.
  
  

If you are not already doing so, consider running the Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.